Conventionally, electric vehicles (EVs) and hybrid vehicles (HVs) are driven by using motor generators powered by on-board batteries. It is more efficient to use a high power supply voltage to drive a high speed and high output motor generator. In many cases, therefore, a boosting converter is used to raise a battery voltage and supply an obtained boosted voltage to the motor generator via an inverter. Since the boosted voltage differs depending on the output torque of the motor generator, feedback control of the boosting converter is performed in order to provide a proper boosted voltage. To control the boosted voltage more properly, a reactor current that flows through a reactor in the boosting converter is measured, and feedback control is performed until the reactor current attains a target value.